nslookup will just resolve the first entry, ie 126.96.36.199 app.oracle.com app, but the second entry will be skipped over, so when you do a nslookup for app.oracle.com, it will succeed, but a nslookup for dbc.oracle.com would fail.
If you want to resolve both names with the same IP, then you need to merge them into the same entry, ie
188.8.131.52 app.oracle.com app dbc.oracle.com dbc
So this is allowed in EBS? or This is not the reason why RDA test failed for this item?
We have some failed items for our RDA health check
Health Check/Validation for "Oracle E-Business Suite Release 12 (12.1.1) Preinstall (Linux x86 and x86_64)"
A00420 DNS Lookup FAILED
A00420 This rule checks that the host is registered correctly in the Domain Name Server (DNS).
The DNS server failed to resolve the name using IP address.
I am not sure what test RDA is performing. A DNS test usually check that a hostname resolves correctly to an IP, but it might go further and also do a reverse lookup, ie do a lookup on the IP and get the hostname back. This test would fail in many systems that don't have reverse dns configured. RDA might be doing this test as it appears to be checking for the IP address, ie
DNS Lookup FAILED
nslookup app.oracle.com should be successful and return the IP address, but nslookup 184.108.40.206 will not resolve if its just added to /etc/hosts
It needs to be registered in the DNS server that is pointed to in /etc/resolv.conf
Check with your network admin whether your DNS supports reverse lookup and if so, whether it has the appropriate zone config with the arpa entries. FYI, Amazon R53 DNS server does not support reverse lookup in case you are using that.
We have also another instance in EC2. But it is working good.
Well maybe it will fail RDA test as well, but we do not have problem with it
Still it has error in nslookup?
[root@erp ~]# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
220.127.116.11 erp.oracle.com erp
[root@erp ~]# cat /etc/sysconfig/network
[root@erp ~]# cat /etc/resolv.conf
# Generated by NetworkManager
search ec2.internal oracle.com
[root@erp ~]# nslookup erp.oracle.com
** server can't find erp.oracle.com: NXDOMAIN
So how what do I do to make it pass?